PLANAR DIFFUSION IN GALLIUM-ARSENIDE FROM TIN-DOPED OXIDES

A new technique for the fabrication of planar junctions in gallium arsenide, by diffusion from tin-doped silicon dioxide layers, has been investigated. It has been found that the doped oxide should contain less than 10% by weight of tin to prevent the occurrence of molten phases at the diffusion temperature (~1010 C). Under these conditions, the junction depth increases as the square root of diffusion time for thick oxides and short diffusion times. However, the junction depth can also decrease with increasing diffusion time due to dopant depletion in the oxide if the oxide is thin and the diffusion time is large. Planar diffusions from tin-doped oxides have been performed in evacuated quartz ampuls, with no arsenic overpressure, using phosphosilicate glass films as diffusion masks. Lateral diffusions of less than twice the junction depth have been achieved by using masks with 15% by weight of P2O5. These diffusions have been performed under conditions that appear to be more severe than those expected during open-tube diffusion. Thus, the results indicate that the doped oxide diffusion technique should be suitable for the development of an open-tube planar diffusion process for the fabrication of gallium arsenide devices and integrated circuits. © 1979, The Electrochemical Society, Inc. All rights reserved.